1. Field of the Invention
The present invention relates to an image pickup apparatus that includes an image pickup unit capable of outputting, as pixel information, an electrical signal after photoelectric conversion from a pixel arbitrarily designated as a read target among a plurality of pixels for imaging.
2. Description of the Related Art
Conventionally, in the medical field, endoscope systems are used when observing the inside of organs of a subject. In an endoscope system, typically, an in-vivo image is picked up by inserting an elongated flexible insertion unit into the body cavity of a subject, such as a patient, emitting the white light to a living tissue in the body cavity via the inserted insertion unit, and receiving the reflected light by the image pickup unit at the tip of the insertion unit. The in-vivo image picked up in this manner is displayed on the monitor of this endoscope system. A user, such as a doctor, observes the inside of the body cavity of the subject via the in-vivo image displayed on the monitor of the endoscope system.
In the endoscope field, a narrow band imaging system has been proposed that uses the special illumination light whose spectral characteristics are narrow-banded compared with the white illumination light used in a conventional RGB frame sequential system (for example, see Japanese Patent Application Laid-open No. 2002-095635). In the narrow band imaging system, capillary vessels in mucosal surface layers and pit patterns are enhanced by emitting light in two bands, i.e., narrow-banded blue light and green light that are easily absorbed by hemoglobin in blood, which contributes to the early detection of bleeding sites or tumor sites that are sites to be detected. Moreover, a fluorescent substance that is originally present in a living tissue and has a spectrum in the range of green or red or a labeling substance that is introduced into the subject and emits red fluorescence or green fluorescence is detected by emitting blue excitation light or violet excitation light having a shorter wavelength than blue.